Search

Frozen thawed ram spermatozoa must be deposited directly into the uterus via laparoscopy as they are unable to traverse the cervix in sufficient numbers to achieve acceptable fertility. Seminal plasma has been heralded as a possible solution to this problem, as it appears to enhance sperm cervical transit. However, the mechanism by which seminal plasma, or indeed cryopreservation, alters spermatozoa to subsequently influence cervical transit is unknown. This thesis explores how seminal plasma and cryopreservation affect the structure and function of ram spermatozoa, with the ultimate aim of improving the in vivo performance of cryopreserved ram semen. The findings of this thesis demonstrate that the physiological process of ejaculation and the artificial practice of cryopreservation significantly alter the molecular profile and function of spermatozoa. Seminal plasma exposure confers additional proteins, alters the sperm glycocalyx, protects spermatozoa from immune cells and regulates the timing of capacitation. Cryopreservation also alters the sperm proteome and glycocalyx, possibly increasing susceptibility of this sperm type to dynamic environmental pressures within the female reproductive tract. Further investigation of the degree to which BSPs benefit ram spermatozoa in the female tract is warranted given their significant effects on sperm cryosurvival and physiology demonstrated herein. The importance of this protein family in ram sperm physiology offers a potential avenue for future improvements in the fertility of frozen thawed ram spermatozoa following cervical insemination.

International audience; Binder of Sperm Proteins (BSPs) are the most abundant seminal plasma protein family in the ram and bull. They have been extensively studied in the bull but less is known about their function in ovine seminal plasma and current knowledge suggests that BSPs may have different effects in these two species. In the bull, they facilitate capacitation and destabilize the sperm membrane during in vitro handling, whereas in the ram, they appear to stabilize the sperm membrane and prevent cryopreservation-induced capacitation-like changes. Further investigation into the effects of BSPs on ram spermatozoa under capacitating conditions is required to further clarify their physiological roles in the ram. We investigated the effects of Binder of Sperm Proteins 1 and 5 on epididymal ram spermatozoa in conditions of low, moderate, and high cAMP. BSPs had minimal effects on sperm function in low-cAMP conditions, but caused significant changes under cAMP upregulation. BSP1 stabilized the membrane and qualitatively reduced protein tyrosine phosphorylation, but significantly increased cholesterol efflux and induced spontaneous acrosome reactions. BSP5 slightly increased spontaneous acrosome reactions and caused sperm necrosis. However, BSP5 had minimal effects on membrane lipid order and cholesterol efflux and did not inhibit protein tyrosine phosphorylation. These findings demonstrate that under maximal cAMP upregulation, BSP1 affected ram spermatozoa in a manner comparable to bull spermatozoa, while BSP5 did not. Summary Sentence Binder of Sperm Proteins originating from seminal plasma play both pro- and decapacitating roles in ram spermatozoa.

National audience